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When Anna Purgar discovered she had an extended family member buried in an unmarked mass grave on the grounds of Tokanui Psychiatric Hospital it began two years of research that revealed some awe-inspiring stories.

The investigation into the mass grave began with a search for Mary Lane-Ambrose, the great grandmother of her sister-in-law.

"We couldn't find her burial anywhere. My sister-in-law and I had been looking all over the place and all we got was somewhere in Te Awamutu," Anna said.

A Te Awamutu council staffer could find no record of Mary but suggested Tokanui, where Mary was known to have lived for a while.

"She came back and said she was on the death register at the hospital. That kicked it off and I thought 'hmmmm, I have to find out about this place'."

Anna checked online and what she found were some appalling photos of the hospital cemetery.

"It was just a concrete block with '500 souls buried here'. I got off the internet and absolutely felt ill. Absolutely angry. You could see dead sheep and cows had been in it."

She began meticulous investigation of the hospital's death register, NZ Death index, NZ Births Deaths and Marriages and records of council cemeteries and progressed to FindAGrave, a website devoted to burial records.

Before long she had enough information to begin inputting information into FindAGrave to help others track down their relatives.

"Within days I had people contacting me; 'did I know any information? was I related to the people?'," Anna said.

"I decided to see what I could do about getting the stock out of the paddock. I talked to the farm owner at the time who was quite appalled about the state of the cemetery."

Between the two they contacted the Department of Conservation which started the ball rolling.

Anna began to do profiles of the deceased.

One profile revealed the startling story of William Nimmo, who was denied a multi-million-pound inheritance due to his mental disorder.

"In Scotland some lawyers had in trust an amount of money that was to be held for 100 years. It had been sitting accumulating millions. This was dated back in the 1700s," Anna said.

"It was only to be given to the next of kin. There was only one left and these lawyers had to go looking for him."

Nimmo was the last living relative of Pieter Teyler Vanderhulst, and papers-past record the man's story.

A copy of NZ Truth from 1929 reads: "the only result of the efforts made by the Government to investigate this claim of the unfortunate man, had been to announce that Nimmo has lost his memory".

Nimmo had emigrated from Scotland in the early 70s, but as Truth recalls the "healthy young pioneer" was "doomed to disappointment, for instead of receiving word of the anxious departure of his bride, he had to face the heart-wrenchings of a jilter lover".

The 1929 article attributes this as laying "the seeds of mental decay" which would one day cost him millions.

Anna remembers another woman born in Russia who was adopted by an English businessman. After his death the family emigrated to New Zealand, only for the wife and adopted daughter to be committed to Tokanui.

"By the end all she had was a Russian costume that must have belonged to her mother at some stage," Anna said.

Reasons for commitment to the asylum included post-natal depression and those with dementia.

Many of the inmates were immigrants, who Anna said suffered without the support networks of home.

"Another very interesting case is a young married woman who was admitted to Porirua Hospital not long after giving birth to her only child, a daughter.

"Years later this daughter became a nurse. I followed her through the electoral roll and it showed her being registered in Tokanui/Waikato, possibly working at Tokanui Hospital as a nurse."

The daughter married and left the Waikato not long after the death of her mother, but records of the daughter's will and husband's World War I and II service file show the family continued to pay for her upkeep at Tokanui for 27 years until her death.

Working almost full-time for free, Anna is finally approaching finalising the list of 456 individuals buried in the plot. She has also been instrumental in seeing a memorial wall constructed on the site.